Micro-electromechanical sensor

• US 7,047,814 B2
• Filed: 07/17/2002
• Issued: 05/23/2006
• Est. Priority Date: 07/17/2001
• Status: Active Grant

• Current Assignee: SMC Kabushiki Kaisha
• Original Assignee: Redwood Microsystems, Inc.
• Inventors: Cahill, Sean, Henning, Albert K., Nystrom, Norm, Mauger, Phil, Zias, Art
• Primary Examiner(s): MCCALL, ERIC SCOTT
• Application Number:
  US10/198,304
• Publication Number:
  US 20030072127A1
• Time in Patent Office: 1,406 Days
• Field of Search: 737/18, 737/24, 361/283.4
• US Class Current: 73/718
• CPC Class Codes: G01L 1/148 using semiconductive material, e.g. silicon
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm

Abstract

A force or pressure transducer is disclosed. In one embodiment, the transducer has a substrate, a dielectric material disposed on the substrate, a spacing member disposed on the dielectric material, and a resilient element disposed on the dielectric material and the spacing member. A portion of the resilient element is separated from the dielectric material, and a portion of the resilient element is in contact with the dielectric material. The contact area between the resilient element and the dielectric material varies in response to movement of the resilient element. Changes in the contact area alter the capacitance of the transducer, which can be measured by circuit means.

Claims

1. A device, comprising:

a substrate configured to act as a first electrode of a capacitor;

a resilient element, configured to act as a second electrode of the capacitor, at least a first portion of which is secured at a position spaced from the substrate by a predetermined gap;

a layer of dielectric material disposed between the substrate and the resilient element, said layer having a thickness corresponding to said predetermined gap; and

a spacing member configured to separate a second portion of the resilient element from the substrate by a distance greater than said predetermined gap to define an effective electrode area of the capacitor corresponding to an area wherein the substrate and resilient element are separated by said predetermined gap, the effective electrode area chancing in response to movement of the resilient element relative to the substrate and resulting in a change in capacitance of the capacitor.

2. The device of claim 1, wherein said spacing member is configured and dimensioned to provide a predetermined tension in said resilient element.

3. The device of claim 1 or claim 2, wherein said layer of dielectric material is disposed on the substrate and said spacing member separates said second portion of said resilient element from said dielectric material.

4. The device of claim 3, wherein said spacing member is configured to separate a central portion of the resilient element from the layer of dielectric material such that a peripheral portion of the resilient element is in contact with the layer of dielectric material.

5. The device of claim 3, wherein said spacing member is configured to separate a peripheral portion of the resilient element from the layer of dielectric material such that a central portion of the resilient element is in contact with the layer of dielectric material.

6. The device of claim 3, wherein said spacing member comprises:

a first portion configured to separate a central portion of the resilient element from the layer of dielectric material; and

a second portion configured to separate a peripheral portion of the resilient element from the layer of dielectric material such that an intermediate portion of the resilient element is in contact with the layer of dielectric material.

7. The device of claim 3, wherein a first surface of the resilient member is configured to be exposed to a first fluid, and wherein said device further comprises an opening defined by the substrate so as to expose a second surface of the resilient member to a second fluid.

8. The device of claim 7, further comprising a fixed boundary chamber disposed on the substrate opposite the resilient member for containing the second fluid.

9. The device of claim 7, further comprising a variable boundary chamber disposed on the substrate opposite tile resilient member for containing said second fluid.

10. The device of claim 1 or claim 2, wherein a layer of dielectric material is disposed on a surface of the resilient element facing the substrate.

11. The device of claim 10, wherein said spacing member is configured to separate a central portion of the layer of dielectric material from the substrate such that a peripheral portion of the layer of dielectric material is in contact with the substrate.

12. The device of claim 10, wherein said spacing member is configured to separate a peripheral portion of the layer of dielectric material from the substrate such that a central portion of the layer of dielectric material is in contact with the substrate.

13. The device of claim 10, wherein said spacing member comprises:

a first portion configured to separate a central portion of the layer of dielectric material from the substrate; and

a second portion configured to separate a peripheral portion of the layer of dielectric material from the substrate such that an intermediate portion of the layer of dielectric material is in contact with the substrate.

14. The device of claim 7, wherein said first fluid has a first pressure, and said second fluid has a second pressure, whereby the contact area between said resilient element and said substrate changes as a function of the difference between said first and second pressures.

15. A device, comprising:

a substrate configured to act as a first electrode of a capacitor;

a resilient element, at least a portion of which is secured at a position spaced from the substrate by a predetermined gap, configured to act as a second electrode of the capacitor; and

a spacing member disposed between the substrate and resilient element supporting a portion of the resilient element at a distance from the substrate greater than said predetermined gap to define an effective electrode area of the capacitor corresponding to an area wherein the substrate and resilient element are separated by said predetermined gap, the effective electrode area changing in response to movement of the resilient element relative to the substrate and resulting in a change in capacitance of the capacitor.

16. The device of claim 15, wherein said spacing member is configured to provide a predetermined tension in the resilient element.

17. The device of claim 15, further comprising a dielectric disposed between the substrate and resilient element to define said predetermined gap, wherein said resilient element is secured at said predetermined gap over a minimum effective electrode area.

18. The device of claim 17, wherein said dielectric comprises a layer disposed on a surface of the substrate and the effective electrode area comprises a variable area of contact between the dielectric material and the resilient element.

19. The device of claim 18, wherein the variation in said variable area of contact is effected by a pressure difference across said resilient element.

20. The device of claim 19, wherein said dielectric comprises a layer disposed on a surface of the resilient element, and the effective electrode area comprises a variable area of contact between the substrate and the dielectric material.

21. The device of claim 15, wherein the spacing member is configured to separate a central portion of the resilient element from the substrate.

22. The device of claim 15, wherein the spacing member is configured to separate a peripheral portion of the resilient element from the substrate.

23. The device of claim 15, wherein the spacing member comprises:

a first portion configured to separate a central portion of the resilient element from the substrate; and

a second portion configured to separate a peripheral portion of the resilient element from the substrate.

24. The device of claim 15, wherein said movement occurs in response to a change in force applied to the resilient element, and the change in the capacitance is a function of said change in force.

25. The device of claim 15, wherein said movement occurs in response to a change in pressure acting on the resilient element, and the change in capacitance is a function of said change in pressure.

26. The device of claim 15, wherein said movement occurs in response toe change in acceleration acting on the device, and the change in capacitance is a function of said change in acceleration.

27. The device of claim 15, wherein a first surface of the resilient element is configured to be exposed to a first fluid, and the substrate defines an opening so as to expose a second surface of the resilient element to a second fluid.

28. The device of claim 15, wherein said resilient element has a non-uniform thickness.

29. The device of claim 15, wherein the resilient element is configured to provide at learn a minimum effective electrode area.

30. The device of claim 15, wherein the spacing member defines a void between the resilient element and the substrate.

31. The device of claim 30, wherein said void comprises a vacuum.

32. The device of claim 30, wherein said void contains a fluid at an initial predetermined pressure.

33. A device comprising;

a substrate configured to act as a first electrode of a capacitor,

a spacing member disposed on the substrate; and

a resilient element configured to act as a second electrode of the capacitor, said resilient element tensioned over said spacing member and secured with the substrate, a portion of said resilient element being spaced from the substrate at a predetermined distance to define an effective capacitance area that varies in response to movement of said resilient element such that a capacitance change effected by said movement may be sustained between said substrate and resilient element.

34. The device according to claim 33, further comprising a dielectric material having a thickness disposed between the substrate and resilient element, wherein said thickness corresponds to said predetermined distance.

35. The device according to claim 33, wherein said resilient element is configured to provide at least a minimum effective capacitance area.

36. A device, comprising:

a substrate configured to act as a first electrode of a capacitor;

a resilient element, a first portion of which is spaced from the substrate by a predetermined gap, said resilient element configured to act as a second electrode of the capacitor; and

a spacing member disposed between the substrate and resilient element supporting a second portion of the resilient element at a distance from the substrate greater than said predetermined gap to define an effective electrode area of the capacitor corresponding to said first portion, the spacing member being configured and dimensioned such that the resilient member is tensioned thereover and the effective electrode area changes in response to movement of the resilient element relative to the substrate resulting in a change of capacitance.

37. The device of claim 36, wherein said substrate comprises a dielectric material with an electrode layer deposited thereon.

38. The device of claim 37, wherein a layer of dielectric material is deposited over said electrode layer, said layer of dielectric material having a thickness corresponding to said predetermined gap and said resilient element is secured to the dielectric layer over a minimum effective capacitance area.

39. The device of claim 36, wherein a layer of dielectric material is deposited on the resilient element between said resilient element and the substrate, said layer of dielectric material having a thickness corresponding to said predetermined gap and said dielectric layer is secured to the substrate over a minimum effective capacitance area.

41. The device of claim 37, wherein said substrate dielectric material is chosen from a group comprising an insulator, an insulator over silicon and SiO₂ over silicon.

42. The device of claim 38 or 39, wherein said layer of dielectric material is chosen from a group comprising silicon, polysilicon, an insulator, an insulator over silicon, an insulator over polysilicon and SiO₂ over silicon.

40. A device, comprising:

a substrate configured to act as a first electrode of a capacitor;

a layer of dielectric material disposed on the substrate;

a resilient element disposed on the layer of dielectric material and configured to act as a second electrode of the capacitor; and

a spacing member configured and dimensioned to separate a portion of the resilient element from the layer of dielectric material to define a first contact area between the resilient element and the layer of dielectric material and such that the resilient element is tensioned thereover, the contact area changing in response to movement of the resilient element relative to the substrate and resulting in a change in capacitance of the capacitor.

43. A device, comprising:

a substrate configured to act as a first electrode of a capacitor;

a resilient element, a first portion of which is spaced from the substrate by a predetermined gap, said resilient element configured to act as a second electrode of the capacitor;

a layer of dielectric material is disposed on the resilient element between said resilient element and the substrate, said layer of dielectric material having a thickness corresponding to said predetermined gap and being secured to the substrate over said first portion; and

a spacing member disposed between the substrate and said layer of dielectric material supporting a second portion of said layered dielectric material and the resilient element at a distance from the substrate greater than said predetermined gap to define a minimum effective electrode area of the capacitor corresponding to said first portion, the spacing member being configured and dimensioned such that the resilient member is tensioned thereover and the effective electrode area changes in response to movement of the resilient element relative to the substrate resulting in a change of capacitance.